Mesomorphic behaviour and polymerisation of temperature-sensitive acrylate liquid crystals

The synthesis, mesomorphic and polymerisation behaviour of two new compounds (3 and 5) incorporating, either a fluorene or an hexaphenylene aromatic core with, respectively, and either two or six hexyloxy-chains terminated with an acrylate group are reported for the first time. The fluorenone-based diacrylate monomer 3 exhibits a thermotropic nematic liquid crystalline phase and possesses good thermal stability within 200 °C, with no detectable crosslinked polymer network formed. In contrast, the triphenylene-based hexa-acrylate monomer 5 shows no observable melting point on heating, even up to 350 °C, due to spontaneous thermal polymerisation and rapid crosslinking to create an infusible covalently bonded, highly crosslinked polymer network before melting could occur. This short study highlights the critical balance between temperature-sensitive phase behaviour and polymerisation dynamics for designing and synthesising liquid crystalline monomers (Reactive Mesogens).